(1) Field of the Invention
The present invention relates to the field of prosthetics, and more particularly to vacuum assisted prosthetic sockets and related methods.
(2) Discussion of Related Art
Amputees use prosthetic devices on their residual limbs using various vacuum or suction arrangements that include the use of liners that are worn between the residual limb and the prosthetic socket. When an amputee walks air inside the socket allows the socket to fall away from the amputee during swing phase (the time the prosthesis is in the air between steps) causing an accelerated impact of the residual limb and the bottom of the socket when the heel hits the floor. By removing the air in the socket the prosthesis is held closer to the residual limb during swing phase reducing the accelerated impact at heel strike. There are many ways to remove the air and several different expulsion valves on the market. Most are installed in the walls of the socket. This is not the most appropriate placement. A valve housed in the distal or bottom of the socket will expel the most air as the amputee's weight at heel strike is directed downward towards the distal portion of the socket.
A known configuration includes the use of a one-way valve provided at a distal end of a socket so that air between the distal end of the residual limb may be pushed through the one-way valve until the residual limb and associated liner are fully inserted into the socket. The one-way valve is then in a closed condition.
To maintain the sub-atmospheric pressure or vacuum at the distal end of the socket, sealing sleeves and other arrangements may be used to prevent influx of air around the distal end of the residual limb and into the distal end of the socket. With a vacuum suspension system, any significant loss of vacuum may result in separation of the prosthetic socket from the residual limb.
Providing a vacuum reservoir chamber maintained at sub-atmospheric pressure and in communication with a prosthetic socket may aid in maintaining a partial vacuum within the socket to compensate for variations in volume of the residual limb while the prosthetic socket is worn and to compensate for air leakage around the residual limb. An integrated system may include vacuum pressure sensors and an evacuation device carried by the prosthetic socket.
U.S. published patent application No. U.S. 2001/0005798 discloses a reservoir maintained at sub-atmospheric pressure mounted on a pylon of a prosthetic device and communicating with the interior of the prosthetic socket via a conduit connected to the reservoir. This arrangement may be unwieldy and adds weight to the prosthetic device suspended from the prosthetic socket.
U.S. published patent application No. 2004/0260403 to Patterson et al. provides an integrated vacuum chamber socket system without any additional electronics (e.g. sensors, pump etc.) to maintain the vacuum within the chamber. However, this configuration may result in leakage of air into the socket that can reduce the vacuum within the vacuum chamber. Also, U.S. published patent application No. 2008/0086218 discloses a vacuum chamber socket system that includes a rigid shell or socket having an integrated vacuum reservoir chamber that may be distally located and that shares a distal common wall with a receiving portion of the socket. The common wall includes a vacuum transfer port having a one-way or non-return valve disposed therein which allows the receiving portion to communicate with the chamber. Such systems require a complicated manufacturing process to form the integrated chamber and the patient may need special skills to don the socket.
Further, there are many different types of one-way valves including spring and duckbill type valves. Spring valves use a spring to resist the air from traveling in one direction while allowing it to travel in the other. The disadvantage to spring valves is the air must accumulate enough force to overpower the spring and open the valve. The consequence of this is that the spring will close the valve before most of the air escapes the socket. This is called cracking pressure. The lowest limit for spring expulsion valves used in prosthetics is about 2 psi.